1. Field of the Invention
The present invention relates generally to shutter speed setting apparatus for photographic cameras and, more particularly, to a shutter speed setting apparatus suitable for use in rewriting as required the shutter speed which is manually set on the photographic camera.
2. Description of the Prior Art
In general, modern photographic cameras include a plurality of one-chip microcomputers (hereinafter referred to as "CPU" or "CPUs") to provide for multiple functions which enable various kinds of settings. On the other hand, setting keys or switches corresponding to the various kinds of settings need to be disposed within an extremely narrow space. It is therefore necessary to minimize the required number of these setting keys or switches.
For this reason, it has been proposed that small setting keys are used to perform various kinds of settings by a combination of a plurality of key inputs.
In a typical example, if an up key is depressed while a shooting mode setting key is being depressed, a programmed AE shooting mode, an aperture-priority AE shooting mode, a shutter-priority AE shooting mode, and a manual shooting mode can be cyclically selected in a predetermined order. In a state wherein the shutter-priority AE shooting mode is selected, the shooting mode setting key is released and the up key is released. Then, if the up key or a down key is depressed, the shutter speed is increased or decreased in step-by-step fashion so that a desired set value of the shutter speed can be selected.
In the above-described example, however, although the number of setting keys can be reduced, the time period required for a shutter speed setting operation is extended. For this reason, there has been a demand for a reduction in the length of such a period with a view to improving the operability of a photographic camera.
As another example, in the manual shooting mode or the shutter-priority AE shooting mode, there is a case where fill-in flash is performed after photographs have been taken in daylight at manually set shutter speeds and without using any flash unit. In this case, if the manually set shutter speed is higher than a flash synchronization speed, the former shutter speed is forcibly changed to a speed which is no higher than the flash synchronization speed. This eliminates the need to manually set the shutter speed at the time of fill-in flash and therefore enables a certain amount of reduction in the aforesaid time period required for a shutter speed setting operation.
However, if, after such fill-in flash, photographing is continued without using any flash unit, it may become necessary to increase the shutter speed. In this case, photographing is commonly continued at a shutter speed near the one which is set before the shutter speed is forcibly decreased. Therefore, the up key needs to be depressed to increase the shutter speed in step-by-step fashion to a desired shutter speed from the forcibly decreased shutter speed which is slower than the flash synchronization speed. This increases the time period required for the shutter speed setting operation.
In another case where a shutter speed S is manually set to 1/1,000 seconds, the shutter speed S may be forcibly rewritten with 1/100 seconds (a temporarily set value S') by turning on a flash switch of the flash unit. In this case, when the shutter speed S is to be decreased to 1/60 seconds by depressing the down key, the down key must be depressed four times in the order of 1/1,000 seconds, 1/500 seconds, 1/250 seconds, 1/125 seconds, and 1/60 seconds. In addition, the shutter speed of 1/100 seconds is continuously displayed until 1/60 seconds is reached. This requires a time-consuming setting operation.